WASHINGTON - Catholic bishops have emerged as a formidable force in the health care overhaul fight, using their clout with millions of Catholics and working behind the scenes in Congress to get strong abortion restrictions into the House bill.

They don't spend a dime on what is legally defined as lobbying, but lawmakers and insiders recognize that the bishops' voices matter — and they move votes. Representatives for the bishops were in House Speaker Nancy Pelosi's Capitol suite negotiating with top officials last Friday evening as they reached final terms of the agreement. Earlier in the day, Pelosi, a Catholic and an abortion rights supporter, had been on the phone to Rome with Cardinal Theodore E. McCarrick, Washington's former archbishop, on the subject.

It wasn't the first time a high-ranking Catholic had weighed in with a key player on writing strict abortion curbs into the health measure. Boston's Cardinal Sean P. O'Malley personally appealed to President Barack Obama about it near the church altar at the early September funeral for Sen. Edward M. Kennedy, D-Mass. Bishops quietly called their congressmen and senators to weigh in.

"The Catholic Church used their power — their clout, if you will — to influence this issue. They had to. It's a basic teaching of the religion," said Rep. Bart Stupak, D-Mich., a leading abortion foe and architect of the health measure's restrictions.

It was Stupak who told Pelosi last Friday that if she wanted a deal on the health bill, she'd be well advised to invite the bishops' staff, who were already in his office, to her table. "I said, 'Well, they're here, and they're one of the key groups you want to have on your side, so why don't we just bring them in and work this out," Stupak said.

Pelosi did, and the result was a final measure that — much to the outrage of abortion rights supporters — bars a new government-run insurance plan from covering abortions, except in cases or rape, incest or the life of the mother being in danger, and prohibits any health plan that receives federal subsidies in a new insurance marketplace from offering abortion coverage. If women wanted to purchase abortion coverage through such plans, they'd have to buy it separately, as a so-called rider on their insurance policies.

The outcome has put Obama and Democratic leaders — already struggling for consensus on the complex and politically tricky health measure — in a tough spot. Democratic abortion foes in the Senate vow they won't support health legislation that omits the strict restrictions approved by the House, while abortion rights champions say they can't possibly vote for a bill that contains them.

Obama suggested Monday that he wants to strike a balance that doesn't allow backdoor federal funding of abortions but preserves women's insurance choices. For now, however, no such middle ground has been identified, and the bishops have served their notice that they will be a player — perhaps the dominant one — in the final outcome.

The U.S. Conference of Catholic Bishops, the church's Washington-based advocacy organization, which is staffed by more than 350 lay people, derives its power in large part from the sheer number of Catholics in this country — 68 million — but also from the special moral and religious standing of its members. Many of them are in regular contact with lawmakers, weighing in on issues from immigration policy to benefits for low-income people.

The group distributed fliers to every parish in the nation asking people to pray for abortion restrictions and to call their congressmen and senators asking them to "fix these bills with pro-life amendments."

And in recent days, the conference staff got elbow-deep in the legislative machinations on the health measure, even having bishops intervene with Republicans — who were loath to help Democrats pass their bill — to make sure they supported the abortion provisions.

Kathy Saile of the conference said Democratic leaders were willing to listen to the group because it has been in favor of Democrats' broader push for a health overhaul.

"We stayed in the conversation until the end, because the bishops have always been adamant about the need for genuine health care reform and want to see health care reform happen," Saile said.

Another factor that undoubtedly helped: Democrats are keenly aware of the power of Catholic voters, more than 50 percent of whom embraced Obama in the 2008 election. That was a substantial swing after Catholics had eschewed the 2004 Democratic presidential candidate, Sen. John Kerry of Massachusetts, who is Catholic.

Said Saile, "This was a lot of members of Congress listening to their constituents."

The outcome left abortion-rights supporters, who couldn't muster enough votes in the House to head off Catholic abortion foes' intervention, fuming.

The bishops "essentially got signoff. They dictated this, and it's totally inappropriate — it's blatant interference between church and state," said Eleanor Smeal of the Feminist Majority. "The women's movement and the pro-choice forces feel like they were had."

Rep. Lynn Woolsey, D-Calif., a leading liberal, suggested Tuesday that the IRS should investigate the conference's tax-exempt status, given its intense lobbying on the health measure.

And Rep. Diana DeGette, D-Colo., a prominent abortion rights supporter who has gathered the signatures of more than 40 representatives who refuse to back a health bill that contains the restrictions, said the bishops had been allowed to overstep their bounds.

"No one group should get to dictate the outcome of legislation in Congress," DeGette said. "Every group should be listened to, but I don't think one group should be given veto authority over what we do."